While there’re multiple tools available for monitoring, ranging from Dan Bernshtein’s daemontools to God, I found that Monit is a pretty balanced solution. On one hand, it’s quite powerful, and on the other – it’s not resource hungry. The only drawback that I found, is that for monitoring a process, the process must have a pid-file saved somewhere. The Monit FAQ states that the programs which don’t have pid-file support should be run with some wrapper which will create it on their behalf.

I wanted to use Monit to monitor Rails’ instances, so if they grow too fat, Monit will take care of that. The problem is that the pid file that the Passenger creates a) doesn’t have a predictable location (there’s something called “generation” or something like that), and b) doesn’t have children, as those processes are detached.

Of course there exists a possibility of patching Passenger for providing such pid files. But, luckily, Passenger provides extension points in form of callbacks which are fired when the application instance is created and when it’s taken down.

It was trivial to use this API to provide pid-file managing. The result of this work was the “passenger_monit” plugin.

There’s a new cool startup called MusiXmatch which provides an easy access to lyrics.
They already have tons of lyrics and they recently opened their API to the alpha testers.
I wrote a basic library for accessing this service. While it’s incomplete, it already provides the most often used functionality such as searching for tracks and getting lyrics.
Example usage:

While the MacOS X iPhone Developer package contains the needed cross-compiling tools, I haven’t found anywhere a clear explanation regarding how the environment should be set for compiling some standard autoconf/automake package.
I’m using the following script (works on the XCode 3.2.2 on Snow Leopard):

Simple, but nice replacement for open-uri library (which uses rather slow Net::HTTP library) which uses libcurl (via curb).
It’s easy to swap the original one just by replacing ‘require open-uri’ with ‘require curb-openuri’. Should work as the original, even with better defaults (which, of course, can be changed).

Several months back I needed to compute NMF of some relatively larges matrices.
Since the native Ruby code was painfully slow, and for some reason even failed to work for some matrices, I decided to write a C implementation which will leverage the GNU Scientific Library (GSL) and then wrap it for using in Ruby application.
It was a neat add-on to the rb-gsl ruby library. What it does is adding NMF module under the GSL::Matrix, and there you have a method nmf which receives a GSL::Matrix and number of columns as a parameter and then returns two matrices.
Since this is an iterative algorithm, the number of runs is limited to 1000, and the desired difference cost metric is set to 10-6.
I tried to contact the author and even posted my code in the issue tracker, but haven’t received any response at the time of writing.
So I decided to create a git-svn mirror on Github and add my changes there.http://github.com/romanbsd/rb-gsl

This simple fix uses the fact, that if the second argument to the ‘add’ method is a symbol, then a generate_message is called, which does all the voodoo of Rails 2.2 I18n.
I tried to contact the original author to no avail, therefore I’ll post it here, hoping that if anyone needs it, it’ll surface on a Google search.
The fix itself is quite simple: